Destructible form



Dec. 12, 1944. GRENEKER 2,364,710

DESTRUCTIBLE FORM Filed March 30, 1.943 2 Sheets-Sheet 1 T5. a- I I INVENTOR 2 24 24 A/u/A/V L. GRENE/fE/P ATTORN 5Y5 Dec. 12,1944. GRENEKER 2,364,710 4 DESTRUCTIBLE FORM Filed March so, 1945 2 sheets-sheet 2 INVENTOR [ILL/AN L GPENE/fE/P ATTORNEYS Patented Dec. 12, 1944 UNITED' STATES PATENT OFFICE 7 2,364,710 DESTRUCTIIBLE FORM Lillian L. Greneker, New York, N. Y. Application March'30, 1943, Serial No. 481,093

7 Claims. (01. 18-45) After the form has served its purpose, that is,

This invention relates to a destructible form which is particularly useful in the manufacture of fuel tanks and cells or articles made of'rubher or other material. It is not concerned withthe particular shape of the form, but merely with its construction, since of course the construction may be used in forms having an infinite variety of shapes and sizes.

The invention may be considered an improvement upon the invention described and claimed in my Patent No. 2,343,292 resulting from my copending application Serial No. 472,559, filed January 16, 1943,in' which is described a hollow form made of a frangible material reinforced by a rope and also (if desired) by a fabric embedded therein, the wall of said form being so thin that pulling out of said rope will reduce the form to pieces which may be withdrawn from the hollow article after it has been made on said form.

The general object of the invention is to provide a form which will be even easier and cheaper to make and lighter than the form described in my aforesaid application, and which will still be strong and rigid and not subject to change of shape under conditions to which it may be subjected in use. Like the form described in the' aforesaid application, the form hereinafter described can be easily destroyed and completely removed from the fuel tank or cell or article which is made on it, even though the opening in the fuel tank or cell or article through which the pieces of the form must be removed is comparatively small.

The present invention achieves the above mentioned object by reinforcing the frangible material of the flat or gradually curved walls of the form with a. suitable board-like material having considerable thickness and stiffness but some flexibility such as Celotex, Sheet Rock, Plasterboard, etc., in combination with a looselywoven fabric and a rope embedded in said frangible material; the wall of the form being so thin where the rope is embedded that pulling the rope out of said form will reduce the form to pieces which may be withdrawn from the hollow article after it has been made on the form. The pieces of board-like material used in making the form are either made small enough to be withdrawn through the opening in the article or, if

' too large to pass through said opening, are broken into pieces small enough to pass through said opening when the form is broken up. Thus, those walls of the form which are fiat or slightly curved, are principally reinforced by the board-like material and fabric embedded therein, and the reinforcing rope is for the most part only embedded in the frangible material around the board-like material and in places where it is more convenient to reinforce the frangible material with the rope than with the board-like material.

after a fuel tank or cell or other article has been made thereon, the pulling out of the rope embedded in the form will destroy the form; where-v upon the pieces and parts thereof, consisting of the rope, the frangible material, the board-like material-and the fabric, can be removed through the opening in the article.

The invention will be understood from the following description, taken in connection with the accompanying drawings, in whichare described and shown a fuel-cell form embodying the invention, and the method of making it. In the drawings, Figs. 1, 2 and 3' are plan views looking at the inside of the cover portion of a mold, and

Figs. 4, 5 and 6 are plan views looking down into the body portion of said mold, showing therein a form embodying the invention undergoing the various steps of its manufacture; Fig. 7 is a perspective view of the body portion of said mold with part' of the form fabricated therein, the wall of the form being broken away to show its construction; Fig. 8 is an end elevation of the body and cover portions of the mold; Fig. 9 is a fragmentary sectional plan view through a corner of the body portion of the mold and a corner of the form fabricated therein; Fig. 10 is a perspective view of the form after it has been fabricated within the mold and removed therefrom; and Fig. 11 is a'sectional view of a wall of the form showing a way in which the rope may be applied to the surface of the board-like material for the purpose of reinforcing it. The samereference characters refer to the same parts throughout the drawings.

As will be apparent form Figs. 1, 2, 3 and 8 the cover portion M of the mold is provided with a boss l6 which defines the opening I! which is to the left in the completed form l8 which is shown inv Fig. 10. From Figs. 4, 5, 6, 7 and 8, it will be apparent that the body portion of the mold consists of sections 20 and 2|. To facilitate proper engagement of the mold sections 20 and 2| with one -an0ther, their engaging surfaces are formed with cooperating shoulders, as shown in the various views; and in order to insure proper placing of the cover section M on the body sections 20' and 2|, upstanding lugs 24 are provided on the upper surfaces of the body sections 20 and 2|, and correspondingly located notches 25 are provided in the cover section [4. The body sections 20 and 2| of the mold may be provided with base members 21 andZB or may be otherwise constructed, so as to facilitate the standing upright of the body sections of the mold in the position shown in Figs. 7 and 8. For holding the body sections of the mold 20 any suitable means may be provided, such as removable metal clamps 30 and 3| cooperating with metal lugs 32 and 33 cast in and projecting and 2| together,

it has sufficient strength it is pulled out of the plaster Figs. 2 and 5. In practice,

section 14 tightly in engagement with the mold sections 20 and 2|, any suitable means maybe used, or merely the weight of the cover section may be relied upon as sufficient. The mold sections may be made of any suitable material such as plaster, cement, metal etc; and the mold can be constructed either according to the dimensions of the form or from a model of the form.

The structure of the form and the methods by which it is made in the mold will now-be described. The frangible material used in the form may be plaster of Paris or any other suitable material, and in the description which follows the term plaster is intended to cover all suitable materials capable of being molded. The board-like material used in the form for rein forcing purposes, in the manner hereinafter described, may be such materials as Celotex or .Sheetrock or Plasterboard or other similar materials which have the property of uniting well with plaster. The fabric, hereinafter referred to, may be of any loosely woven kind such as cheesecloth or what is commonly known as paper burlap" Which I have found to be particularly .satisfactory. The rope (hereinafter referred to) which is used for the double purpose of reinforcing the form and providing means for its ready destruction after the form has served its purpose in the making thereon of a fuel tank or .cell or other article, may be of any cheap kind, provided to stand the strains imposed upon it when during the destruction of the form.

Before fabricating the form within the mold sections I4, 20 and 2!, the inside surfaces of the latter are greased in order to prevent sticking of the plaster thereto, as is customary in the molding of plaster articles. These greased surfaces of the mold sections are then covered with a thin layer of wet plaster, as indicated at 36 in Figs. 1 and 2, and at 31 in Figs. 4 and 5. Pieces of loosely-woven fabric, such as paper burlap, are then applied to the wet plaster and more or'less embedded in it, as represented at 39 and 40 in it'is desirable to cut to pass served its purpose. However, it has been found convenient, satisfactory and time-saving to make some of the pieces of board-like material so large that they would not easily pass through the opening in the completed article corresponding to the opening I! in the form, and then to break up these pieces of board-like material into small enough pieces to pass through said opening when the :form is destroyed. To facilitate the breaking up of such larger pieces of board-like material, it'fha-s been found useful to cut partially through such larger pieces of board-like material, so that it will readily break up into pieces small enough through the opening in the fuel cell after it has been fabricated on the form. The pieces of board-like material used in reinforcingthe portion of the 'form'wliich is made in the-cover section 1'4 are shown inFig. 3 at 42 and '43, it

' being .understood that these sections are partially 'cut through and thereby weakened along'the lines E5 and '46. The piece of reinforcing board-like material used in the bottom of the body portion the fabric.39 and into pieces approximating in size and shape the walls of the mold to which the fabric is to be applied, so that the fabric Will extend substantially completely throughout the area of the plaster. Then a thin layer of wet plaster may be applied to the fabric in order to more completely embed it in the plaster. fabric, so embedded in the plaster, serves .to reinforce the walls of the form and to prevent the Theformation of cracks therein upon drying, as will be hereinafter mentioned. Pieces .of board-like material, such as Celotex, are then pressed against the fabric-reinforced wet plaster which has been applied to the inside surfaces of'the mold sections. Preferably, these pieces of boardlike material, before insertion in the mold, are smeared with wet plaster on the side which is to be applied to the wet plaster in the mold, so

as to improve the bonding of the board-like material to the plaster in the mold. The pieces of board-like material so used for reinforcing the walls ofthe form are cut to such a size that the board-like material will cover the major portions of the Walls of the form to which'they are applied. Such material may be cut into pieces small enough to passthrough the openingin the fuel cell corresponding to the opening H in thefform 18, when the form is broken up "after it has of the mold is indicated in Fig. 6 at '48, it being understood'that this piece of board-like material has been partially cut through and thus weakened along the lines 49, 50 andS-l. The pieces of board-like material used in reinforcing the side walls of "the mold are indicated in Fig. 6 at'53 and '53, and those used-in'reinforcing the end sections of the'form'are shown-at'56 and 51, it being understood that these sections may also be partially out through as "above described in order to facilitate their breaking up and removal when the form isdestroyed after it has served its purpose. In order to hold the'pieces of boardlike material 53 and 54 in their bent condition and firmly in engagement with the wet plaster of the form will then berigid and'sel'f-supporting.

After the reinforcing board-like materialhas thus been applied to the fabric-reinforced wet plaster within the mold sections, .a rope is laid into the wet plaster wholly or partially around the pieces of board-like material, for the double purpose of reinforcing the plaster at those places and providing means for readily destroying the form after it has served its purpose in them'aking of a fuel cell. Fig.3 shows one wayyin which the rope 60 may bellaid in the wet plaster in the cover section 14 of the mold, but it will'be understood thatthe rope maybe laid in other ways "at the discretion of the-maker'of-the form. After the rope Bil, has beenlaid'in the plaster, more wet plasteris applied toJit so as to buryit and cover the edges of the pieces of board-.likematerial. Complete burying of ,thepieces of boardlik material in the plaster'has-been found .not

to be necessary; that is,;the main portion of the inside surface ofthe board likematerial-may be leftbare. In laying the rope in the body portions 20 and 21 of the form, it will'be found convenient and satisfactory to lay it'in the Wet plaster at the verticalcor'ners of the mold and around'the corners at the bottom of the. mold, thereby providing-both for reinforcing the .form

:at'those points and for destruction'of the "form by thelpulling outo'f the rope after the "formhas serve'dits purpose. .'In Fig..6'the'free end .of the rope is indicated at 62. I

Fig. 9 shows in cross section the construction of the form within the body section of the mold at one vertical corner; and makes clear how the walls of the hollow form are reinforced by the While the plaster in the cover section 14 and in the body sections 20 and 2| of the mold is still moist, the cover [4 is applied-to thetop of the body sections 2:! and 2i; and in a short time the plaster in the cover section unites with the plaster in the body sections of the mold. Thus, Within the mold there is madea hollow plaster form the walls of which although thin have very considerable strength owing to the reinforcing action of the fabric, the board-like material and the rope. Moreover, any tendency for the formation of cracks in line board-like material, is prevented by the reinforcing effect of the fabric embodied in the plaster at those places.' the mold for a short time, the cover section I4 is removed; and after removal of the clamps 38 and 3! at each end of the mold sections 20 and 2] the latter are separated, thereby facilitating removingfrom the mold the form l8 shown in Fig. 10. After drying, preferably in a drying room or oven, the form ['8 is complete and ready for use in the manufacture of a seamless fuel tankor cell. The outside surfaces of the form i8 may, if desired, be covered with paper glued thereto, or treated in any other suitable manner, according to the preferences of the users of such forms. Another way of covering .the outside surfaces of the form with sheet material such as paper or cloth, is by laying such paper or cloth over the inside surfaces of the mold at the beginning of the fabricating process; after which the first thin layer of wet plaster is applied to the paper or cloth (instead of directly to the greased inside surface of the mold) and bonding of the paper or cloth to the plaster takes place during the making of the form. When paper or cloth is so used, it will in some cases reinforce the plaster sufliciently to make it unnecessary to embed in the plaster the fabric hereinbefore mentioned.

In some forms, it may be desirable to provide additional reinforcing of a wall of the form. Fig. 11 illustrates a convenient and satisfactory way of providing such reinforcing. As will be obvious from that figure, this reinforcing may be accomplished by laying a rope 65 across the inner surface of one of the pieces of reinforcing board-like material 66 which is bonded to plaster 6! which is reinforced by a loosely-woven fabric 68, all lying within a mold wall 69. A piece of fabric 70, preferably after being dipped in wet plaster, is preferably laid over the rope 65; and then enough wet plaster II is applied to bury the rope 65 and the fabric 10. The plaster 1| dries in the form of a ridge on the inside sur face of the board-like material 66, and owing to the reinforcing nature of the rope 65 the rigidity of the wall of the form at that location is increased. This way of reinforcing the wall of the form may, of course, be used in connection with curved walls as well as fiat walls.

From what has been stated, it will be understood that, after fabrication of the fuel cell on with the edges of the After the plaster has set within' the form l8, it is possible to reach through the opening in the fuel. cell corresponding to the opening I! in the form and to seize the loose end or ends of the ropes which are embedded in the plaster of the form. By pulling the rope or ropes the whole structure of the form may be broken up; and the rope, the pieces of reinforcing board-like material, the reinforcing fabric (when used) and the paper covering (when used) may be readily removed through the opening in the article the form. Any small amount 'of loose plaster or dust or pieces of sheet material or fabric or paper left within the fuel cell can easily be removed by washing or an air blast,

Of course it is not absolutely necessary to provide any opening, such as 11, in a form made in the manner herein described. That is, the form may be made with cases the fuel tank or cell or other article made on the form will have cated upon the form.

It will be understood that various modificaembodying the present invention, without de parting from the spirit of the claims hereto appended.

What is claimed is: r l. A hollow form which in outside shape and on said form, the wall of said form being made of frangible material reinforced by a fabric embedded therein and also by board-like material board-like material and is covered with frangible material.

LILLIAN L. GRENEKER.

corresponding to the opening H in' CERTIFI GATE OF CORRECTI 0N Patent No. 2,562+,71o. December 12, 19M.

LILLIAN L. GRENEKER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows; Page 1, second column, line 59, for "the left" read --be left"; and-that the said Letters Patent should -be read with this correction therein that the same ma; conform to the record of the case in the Patent Office.

Signed and sealed this 20th day of March, A. D. 1915.

Leslie Frazer (Seal) Acting Commissioner of Patents. 

